Target Purple Emperor - Herts & Middx Butterfly Conservation

Target Species ~ Purple Emperor (Apatura iris)

Purple Emperor 2004 - Glen Barnes
Purple Emperor 2004 - Nick Sampford
Purple Emperor 2004 - Nick Sampford

© photo: Glen Barnes

© photo: Nick Sampford

© photo: Nick Sampford

Essential reading! Hertfordshire Purple Emperor Reports can now be downloaded free.


A copy of the The Hertfordshire Biodiversity Action Plan with a section dedicated to the Purple Emperor can be downloaded here

The Purple Emperor is the only butterfly identified in the Thames Regional Action Plan as having High Priority status in Hertfordshire or Middlesex. It is also Hertfordshire BAP Species.


The bright green egg is laid on the upper surface of a sallow/willow leaf (salix sp.) and usually hatches within 16 days.


The tiny caterpillar feeds on sallow/willow leaves into the autumn, usually early November. Winter is spent pressed against a dormant bud or in the fork of a twig on a silk pad. After hibernation, they continue to feed on the sallow/willow leaves. The caterpillar has four skin changes: two before and two after hibernation. After their final moult the caterpillar is 35-40mm long


The pupa is formed during June and hangs from the underside of a leaf. This is the most difficult stage to observe and the exact time of pupation is not known although believed to be between 2 and 3 weeks.


Flight time can be within the period from the 4th week of June to the middle of August at the extremes, but the peak period when most activity in Hertfordshire has been observed is during the middle of July. Their flight is very distinctive as they are large and are one of the few British butterflies to glide. Both the male and female appear dark in flight, although the female is slightly larger. The upperwings of the male can refract a purple sheen when seen at a some angles

Only the White Admiral is in any way similar and this is smaller and is more likely to be seen low down and feeding on nectar, although it may appear brown in certain lights, it is also a distinctly rounded butterfly.
A picture guide to help identify 'high flying' summer woodland butterflies


The Purple Emperor may be seen gliding between gaps in the tree canopy although, occasionally, one will be seen taking salts from the ground or 'waste matter.' The highlight is to see males clashing around the 'master tree.' For breeding, the female uses Salix leaves that are on the shady side or within the crown of the tree. The female usually lays her eggs during the middle of the day.

Where to Look
It is well worth patiently exploring Salix-rich woodland from the end of June, particularly concentrating on tall oaks that stand above the rest of the canopy on high ground or hillocks. Sallows with their characteristic catkins (pussy willow) are highly visible in the spring. Sallows flower before the surrounding leaves have emerged - this is the best time to determine whether a wood is Salix-rich.

Help with monitoring?
There over 15 sites in Hertfordshire and Middlesex where Purple Emperor have been seen since 1999. It is becoming an almost impossible task to monitor them all effectively especially on the peak days of territorial activity. We are always looking to recruit volunteers who will be able to go at short notice to specific sites, on specific days and just watch territories for us. We want to be able to monitor all sites at the same time, so we can gain a greater understanding of populations levels at all sites on the same days. This will also enable us to visit some of the private sites and look for new territories on peak days. The essential requirement will be patience. If you think you can help please contact Liz Goodyear or Andrew Middleton for more details. Training will be given.

If a new site is found it is essential that the owner is informed before the news is made public. Andrew Middleton and Liz Goodyear will be happy to help advise in their capacity as Species Co-ordinators. It is important that landowners, and woodland managers understand the importance of this species and guidance must be given for future management.

The following reports by Liz Goodyear and Andrew Middleton are now available to download free.

The Hertfordshire Purple Emperor 2002
Progress Report 2003
Progress Report 2004 & 2005
The Hertfordshire Purple Emperor
The Hertfordshire Purple Emperor Project
Progress report for 2003
The Hertfordshire Purple Emperor Project
Progress report for 2004 & 2005

Downloads ~ Adobe Acrobat format (PDF) :-

The Hertfordshire Purple Emperor (to 2002)~ published June 2003

Supported by the Hertfordshire Natural History Society

This is the first report and covers the early years of study of the Purple Emperor and its favoured haunts.

The report covers the following aspects of the study:

  • All known historical records and original text relating to Hertfordshire, many previously unpublished, and some concerning additional sightings
  • Survey results and charts for 1999-2002
  • Accounts of each location found to have Purple Emperor, 1999-2002, with personal accounts from many observers (some private woods are not named)
  • Historic and potential areas
  • Notes on the habits of Purple Emperor as observed in Hertfordshire
  • Notes on distribution, weather and climate relating to Purple Emperor in Hertfordshire, U.K. and Eurasia Maintaining and increasing available habitats; addressing the Butterfly Conservation Species Action Plan in Hertfordshire
  • Additional research into the history of the butterfly in Essex

Purple Emperor Project Progress Report for 2003 ~ published April 2004
Supported by the Hertfordshire Natural History Society

This is the second report and covers the continued study of the Purple Emperor in 2003

  • Includes further historic information
  • Notes on detecting the species and behaviour and conservation efforts
  • The report includes details of sightings in Middlesex

Purple Emperor Project Progress Report 2004 and 2005 ~ published February 2006
Supported by the Hertfordshire Natural History Society

This is the third report and discusses the continued study of the Purple Emperor during 2004 and 2005 in Hertfordshire

  • Reports from over 15 sites
  • Includes a new section detailing the history of the Purple Emperor in the Eastern Region
  • Further notes on detecting the species and behaviour and conservation efforts.


Text by Liz Goodyear and Andrew Middleton
March 2010 (updated February 2015)


Please send any records of colonies, singletons or potential sites to:
Liz Goodyear
Telephone: 01920 487066